I saw an article a few years ago, where they said most people disadvantage themselves unknowingly - by not negotiating their salary for their first job out of college harder.

The thinking being that if most people usually move jobs for their current salary +x%, that initial figure has a profound compound effect throughout the rest of your earning career.

Bad advice if your value delivered is 100-200% what you currently earn (which can vary significantly based on the organization into which you deliver it). This can mean the difference between having a boat to retire on or not, after compound interest.